Transcript Determine Time of Death

Death: Meaning, Manner,
Mechanism, Cause and Time
Chapter 11
Death
•
Manner of death can be natural,
accidental, suicidal, homicidal, or
undetermined.
• The most common manner of death is
natural.
• Mechanism of Death is the specific
change in the body that brought about
the cessation of life
2
Determine Time of Death —Livor Mortis
livor mortis:
• Process when body decomposes and blood seeps
down and settles into lower parts of body.
Lividity :
• pooling or settling of blood
in tissues after death.
• Begins 2 hours after death
becomes permanent after 8.
Determine Time of Death —Livor Mortis
Livor mortis can:
• Determine Time of Death
•Within 2-8 hours, can press skin and color
disappears
•Factors affecting lividity
•Ambient temperature, anything that could impede
flow of blood to area
•Reveal the position of the corpse within first 8 hours
•If on back, blood will pool along backside
•Reveal if the body was moved
•If moved, may show dual lividity from first position
and then from second position
Determine Time of Death —Rigor Mortis
Stiffening of the skeletal
muscles after death
•
•
At death, skeletal muscles cannot relax.
Without oxygen, calcium accumulates in these
muscles.
–
•
•
5
Calcium is used by the body to signal muscle
contraction, this accumulation signals the muscles
to contract.
The muscles become stiff.
Rigor mortis starts in the head and works its
way down to the legs.
Determine Time of Death —Rigor Mortis
• 2 -6 hours postmortem (after death), rigor
begins in the head
• 12 hours postmortem, rigor is complete and
throughout the entire body
• 15 -36 hours postmortem, the muscle fibers
begin to dissolve, and softening begins (rigor
mortis starts to end).
• 36 -48 hours postmortem, rigor ends and is
relaxed throughout the entire body.
6
•
Figure 11-8 in book
Determine Time of Death —Rigor Mortis
Factors that affect rigor mortis
– Ambient temperature
• (cold = slow rigor)
– The weight of the body
• (obesity = slow rigor)
– The body’s clothing or lack of it
– Any illness the person had at the time of death
– The level of physical activity at the time of
7
death
– Sun exposure
Determine Time of Death —Algor Mortis
Cooling of the body after
death
• In death a body no longer generates warmth
and begins to cool down.
• To find the standard temperature of a corpse,
a thermometer is inserted into the liver.
• Time of death determined by temperature
calculations is expressed as a range of time.
– Normal body temperature is 98.6°F (37°C)
8
Determine Time of Death —Algor Mortis
Calculations
• First 12 hours after death:
– Body cools 0.78 °C (1.4 °F) per hour
• After 12 hours after death:
– Body cools 0.39 °C (0.7 °F) per hour
• Example
– What is the temperature loss for someone who has
been dead for 12 hours?
9
• 0.78 ° C x 12 hours = 9.36 ° C
Determine Time of Death
—Stomach and Intestinal Contents
• 4-6 hours for stomach to empty contents
into small intestine
10
•
Another 12 hours for the food to leave the
small intestine for the large intestine
•
24 hours for the food to leave the large
intestine
Determine Time of Death
—Stomach and Intestinal Contents
Example –
Determine the time of death from the last
meal if food is found in the small
intestine
Answer: Death occurred 4 - 6 hours after the last
meal
11
Determine Time of Death
—Stages of Decomposition
•
Within 2 days
–
–
–
•
After 4 days
–
–
•
The skin blisters.
The abdomen swells.
Within 6-10 days.
–
–
–
–
12
Cell autolysis begins following death.
Green and purplish staining from blood decomposition.
Marbling appearance on the skin. Discoloration of the face.
The corpse bloats.
Fluids begin to leak from body openings as cell membranes
rupture.
The skin sloughs off.
Eyeballs and other tissues liquefy.
Determine Time of Death —Insects
Forensic Entomology
• Within minutes of a death, certain insects
arrive to lay their eggs on the warm body.
– Blowflies are a common example.
• As a corpse progresses through the stages of
decomposition, other kinds of insects arrive.
13